EJ, sorry to hear about your situation. There was a study recently suggesting the value of vitamin D3 (1000 IU max daily) in helping to prevent colon cancer and obviously, overall diet is also a major factor (avoiding red meat and eating plenty of fresh fruit and vegetables).
Incidentally, Alizyme have a drug to treat both chronic and acute ulcerative colitis, called COLAL-PRED; just ready for PIII. It is a swallowable capsule that releases the steroid only in the lower gut, and is both safer and useable over longer periods than systemic steroids. It is said to be a dramatic improvement over the existing gold standard steroid delivery, and more effective than 5-ASA's.